The advantageous use of light, the visible electromagnetic radiation, as the signal medium in communications and in computer systems is well recognized. Of particular importance is coherent light such as that produced by lasers because of propagation characteristics and bandwidth. Modulation of a laser beam is a rapid and efficient means of information transmission.
Various devices for modulation of a light beam are currently in use. These include semiconductor devices utilizing quantum wells fabricated by molecular beam epitaxy in 3-5 compounds and other switching devices 3-5 compound, quantum well devices have excellent switching characteristics, but their manufacture involves complicated and expensive technologies. There exists a need for a light modulator which is simple in construction and inexpensive which can readily be fabricated in the form of a 2-dimensional array, and, at the same time, which is capable of switching light on and off at gigahertz rate, a rate much larger than that for most conventional devices.
A review of the prior art reveals one device which involves a grating, namely, a surface emitting distributed feedback laser which uses a grating to support the necessary feedback for laser operation. See G. E. Evans, N. W. Carlson, J. M. Hammer, R. A. Bartolini, Laser Focus World, November 1988, p.97; and W. Streifer, D. R. Seifres, R. D. Burnham, IEEE J. Quantum Electronics, Vol. QE-12, No. 7, July 1976. In contrast, the present invention provides for the modulation and control of a beam produced by a laser.